The Cardiovascular Response to Intrapulmonary Pressure Inflation in Dogs Treated with Reserpine,Propranolol,and Phenoxybenzamine

Abstract

Conclusions

Reflex adrenergic responses to IPPI in anesthetized dogs were studied. Phase 4 arterial blood pressure overshoot was abolished by PBZ but not by propranolol indicating a major alpha-adrenergic contribution in the production of the overshoot. Phase 2 reflex tachycardia was blocked by propranolol, as a manifestation of beta-adrenergic blocking effect. PBZ also suppressed the response, although to a lesser degree. A marked myocardial NE depletion was associated with a significant reduction in phase 2 heart rate response and complete abolition of phase 4 arterial blood pressure overshoot to IPPI, when dogs were pretreated with reserpine more than 18 hr prior to the experiment. But reduction in reflex tachycardia was not as marked and the pressure overshoot was normal if the studies were carried out 4–5 hr following reserpine administration. Several possible factors are offered as possible explanations for the “time factor” and for the difference in δHR and δMBP responses in Group A dogs.